AB-FUBINACA (Correctly named AMB-FUBINACA using EUDA nomenclature,^[2] however this name is erroneously associated with MMB-FUBINACA) is a psychoactive drug that acts as a potent agonist for the cannabinoid receptors, with K_i values of 0.9 nM at CB₁ and 23.2 nM at CB₂ and EC₅₀ values of 1.8 nM at CB₁ and 3.2 nM at CB₂.^[3][4][5] It was originally developed by Pfizer in 2009 as an analgesic medication^[6] but was never pursued for human use. In 2012, it was discovered as an ingredient in synthetic cannabinoid blends in Japan,^[7] along with a related compound AB-PINACA, which had not previously been reported.

Its use has been linked to hospitalizations and deaths.^[8][9]

On August 15, 2018, 70 people within the city of New Haven, Connecticut, started overdosing near Yale University campus.^[15]

Most news reports only used the name “K2” which can refer to any synthetic cannabinoid consumed by smoking. One news report did use the name “fubinaca” and this is understood to have meant AB-FUBINACA rather than another analogue.

By the end of the week, the total number of overdosed had risen to over 100 people needing transport to local emergency rooms. Three men were arrested, charged as drug dealers selling synthetic cannabis according to news reports.^[16][17][18] First responders concluded that the overdoses were caused by opiate adulterants, as victims responded to Narcan.^[15] However, later news reports only said that the material had tested positive for the generic “K2” and did not mention charges for distributing or possessing fentanyl in the arrests.

Almost all of the overdoses occurred on the New Haven Green, a large downtown park that is heavily travelled and very popular with the homeless population. There were no deaths reported as a result of the incident after 2 days.^[18]

AMB-FUBINACA is the correct systematic name derived using the EUDA synthetic cannabinoid naming scheme:^[2] N-[(2S)-1-Amino-3-methyl-1-oxobutan-2-yl]-1-[(4-fluoro-benzyl]indazole-3-carboxamide.

AB-FUBINACA is specifically named in the naming scheme briefing as the first example of an attempt to derive a systematic short name from the IUPAC name, by Uchiyama et al. in 2012.^[7] Due to the naming preceding the scheme, the use of AB-FUBINACA has stuck for this compound and the systematic name is less widely used, despite the fact that AB-FUBINACA describes the 1-amino-1-oxobutane (without a methyl at the 3 position) analogue according to the naming scheme.